The present invention relates generally to a new metal/magnetic-ceramic laminate with through-holes and such magnetic-ceramic materials as low temperature sintered ferrites and process thereof. More particularly, the invention encompasses new sintering aids for low temperature sintering of ferrites and process for fabrication of a large area ceramic laminate. The present invention also relates to a magnetic matrix display (MMD) electron beam source, and methods of manufacture thereof.
A magnetic matrix display is particularly, although not exclusively, useful in display applications, especially flat panel display applications. Such flat panel display applications include television receivers, visual display units for computers, especially, although not exclusively, portable and/or desktop computers, personal organizers, communications equipment, wall monitor, portable game unit, virtual reality visors and the like. Flat panel display devices based on a magnetic matrix electron beam source hereinafter may be referred to as Magnetic Matrix Displays (MMD).
Conventional flat panel displays, such as liquid crystal display panels, and field emission displays, provide one display technology. However, these conventional flat panel displays are complicated and costly to manufacture, because they involve a relatively high level of semiconductor fabrication, delicate materials, and high tolerance requirements.
U.S. Pat. No. 5,917,277, (Knox, et al.), issued on Jun. 29, 1999, entitled xe2x80x9cELECTRON SOURCE INCLUDING A PERFORATED PERMANENT MAGNETxe2x80x9d, assigned to International Business Machines Corporation, Armonk, N.Y., USA, the assignee of the instant Patent Application and the disclosure of which is incorporated herein by reference, discloses a magnetic matrix electron source and methods of manufacture thereof. Also disclosed is the application of the magnetic matrix electron source in display applications, such as, for example, flat panel display, displays for television receivers, visual display units for computers, to name a few. Also disclosed is a magnetic matrix display having a cathode for emitting electrons, a permanent magnet with a two dimensional array of channels extending between opposite poles of the magnet, the direction of magnetization being from the surface facing the cathode to the opposing surface. The magnet generates, in each channel, a magnetic field for directing electrons from the cathode means into an electron beam. The display also has a screen for receiving the electron beam from each channel. The screen has a phosphor coating facing the side of the magnet remote from the cathode, the phosphor coating comprising a plurality of pixels each corresponding to a different channel. There are grid electrode means disposed between the cathode means and the magnet for controlling the flow of electrons from the cathode means into each channel. The two dimensional array of channels are regularly spaced on an X-Y grid. The magnet area is large compared with its thickness. The flat panel display devices based on a magnetic matrix electron source is referred to as MMD (Magnetic Matrix Display).
The permanent magnet is used to form substantially linear, high intensity fields in the channels or magnetic apertures for the purpose of collimating the electrons passing through the aperture. The permanent magnet is insulating, or at most, has a low conductivity, so as to allow a field gradient along the length of the aperture. The placement of the beam so formed, on the phosphor coating, is largely dependent on the physical location of the apertures in the permanent magnet.
In operation, these electron beams are directed at a phosphor screen and collision of the electron beam with the phosphor results in light output, the intensity being proportional to the incident beam current (for a fixed final anode voltage). For color displays, three different colored phosphors (such as red, green and blue) are used and color is obtained by selective mixing of these three primary colors.
For accurate color reproduction, the location of the electron beams on the appropriate colored phosphor is essential.
Some degree of error may be tolerated by using xe2x80x9cblack matrixxe2x80x9d to separate the different phosphors. This material acts to delimit individual phosphor colors and also enhances the contrast ratio of the displayed image by making the display faceplate appear darker. However, if the electron beam is misplaced relative to the phosphor, initially the light output from the phosphor is reduced (due to loss of beam current to the black matrix) and this will be visible as a luminance non-uniformity. If the beam is subject to a more severe placement error, it may stray onto a different colored phosphor to that for which it was intended and start to produce visible quantities of light output. Thus the misplaced electron beam is actually producing the wrong light output color. This is called a purity error and is a most undesirable display artifact. For a 0.3 mm pixel, typical phosphor widths are 67 xcexcm with 33 xcexcm black matrix between them.
It will be apparent that a very precise alignment is required between the magnet used to form the electron beams and the glass plate used to carry the phosphors that receive the electron beams. Further, this precise alignment must be maintained over a range of different operating conditions (high and low brightness, variable ambient temperature etc).
A number of other magnet characteristics are also important when considering application for a display, such as, for example:
(a) It is generally accepted that the displayed image is formed by a regular array of pixels. These pixels are conventionally placed on a square or rectangular grid. In order to retain compatibility with graphics adaptors the magnet must thus present the electron beams on such an array.
(b) In operation, the spacing between the grids used for bias and modulation of the electron beam and the electron source determines the current carried in the electron beam. Variations of this spacing will lead to variations in beam current and so to changes in light output from the phosphor screen. Hence it is a requirement that the magnet, which is used as a carrier for these bias and modulation grids, maintain a known spacing to the electron source. To avoid constructional difficulties, the magnet should be flat.
(c) The display will be subject to mechanical forces, especially during shipment. The magnet therefore must retain structural integrity over the allowable range of stresses it may encounter. A commonly accepted level is an equivalent acceleration of about 30 G (294 msxe2x88x922).
(d) Since the magnet is to be used within the display, which is evacuated, it should not contain any organic components which may be released over the life of the display thereby degrading the quality of vacuum or poisoning the cathode.
(e) The magnet should be magnetized in the direction of the apertures, that is the poles correspond to the faces of the magnet.
The manufacture of such a magnet that satisfies the above conditions is not possible by the use of previously known manufacturing methods. Certainly a magnet (ferrite, for example) of the desired size without apertures is readily obtainable but the presence of the apertures causes some problems.
If the apertures in the magnet are to be formed after the ferrite plate has been sintered, either laser or mechanical drilling may be used. However, the sintered ferrite is a very hard material and forming the apertures by this technique will be a costly and lengthy processxe2x80x94unsuitable for a manufacturing process.
Therefore, preferably holes could be formed in the ferrite at the green state before sintering by known punching/drilling methods typical of multi-layer ceramics for microelectronics applications. However, during sintering a number of problems would be anticipated, such as, for example:
The magnet plate will be subject to uneven shrinkage leading to the holes xe2x80x9cmovingxe2x80x9dxe2x80x94an unequal radial displacement from their nominal positions;
The magnet itself is likely to xe2x80x9cbowxe2x80x9d such that it forms a section of a large diameter sphere;
Cracking is likely to occur between adjacent apertures due to the apertures acting as stress concentrators; or
If, to obtain the desired aperture length, multiple thin sheets are stacked on top of one another, misalignment may occur in stacking which could lead to no xe2x80x9cline of sightxe2x80x9d through the apertures.
A further problem is that ferrite is a hard but not a tough material, and the presence of the apertures significantly reduces the mechanical strength of the plate. Thus, during shipment when large shocks may be encountered, complete mechanical failure of the magnet is a distinct possibility.
Hence, it may be necessary to use metal carriers both for mechanical strength and hole positional accuracy. In such a situation, the high temperature stability of the metal carrier materials of choice in the oxidizing sintering ambient needed for ferrite sintering dictates that the sintering temperatures of these materials to below about 1,000xc2x0 C. or even lower. Similarly, the inventive sintering aids for these ferrites also need to produce a dense ferrite with coefficient of thermal expansion (CTE) of about 10xc3x9710xe2x88x926/xc2x0 C. The sintering aids should be such that they do not degrade the magnetic properties of the ferrites.
However, typical sintering temperature for Barium or Strontium or Baxe2x80x94Sr ferrites is above 1300xc2x0 C., therefore efforts have to be made to reduce the sintering temperature or develop materials that will meet the requirements of such applications.
U.S. Pat. No. 4,138,236 discloses a method of bonding hard and/or soft magnetic ferrite parts with an oxide glass. The oxide glass may be applied prior to or after pre-firing or main firing. Finally, the ferrite parts are fused at temperatures in excess of the glass softening point.
U.S. Pat. No. 4,540,500 discloses a low temperature sinterable oxide magnetic material prepared by adding 0.1 to 5.0 percent by weight of glass to ferrite. In some situations, the sintering temperature can be reduced to about 1,000xc2x0 C. or less.
U.S. Pat. No. 4,023,057 discloses a compound magnet for a motor stator having a laminated structure that includes thin, flexible magnets made from permanently magnetizable particles, such as barium ferrite, that are embedded in a flexible matrix, such as rubber. Various laminated arrangements are contemplated for producing more intense magnetic fields and thin metal spacers are used in most laminated structures to collapse the respective fields of the flexible magnetic components to increase the flux density at the resultant poles and to orient the permanent magnetic fields in the magnetic circuit of the motor.
Published Japanese Patent Application No. JP60093742 discloses a display having a focus electrode with a conductive magnetic body and a sputtered metal coating on one surface of the magnet body. The conductivity is required for the focusing electrode to perform its function. The coating is sputtered and so is a thin coating, not substantially adding to the mechanical structure of the magnet. Each of the holes in the magnet has a number of electron beams passing through it.
U.S. Pat. No. 5,932,498, (Beeteson, et al.), issued on Aug. 3, 1999, entitled xe2x80x9cMAGNET AND METHOD FOR MANUFACTURING A MAGNETxe2x80x9d, assigned to International Business Machines Corporation, Armonk, N.Y., USA, the assignee of the instant Patent Application and the disclosure of which is incorporated herein by reference, discloses a magnet-photosensitive glass composite and methods thereof.
U.S. Pat. No. 5,857,883, (Knickerbocker et al.), entitled xe2x80x9cMethod of Forming Perforated Metal/Ferrite Laminated Magnetxe2x80x9d, assigned to International Business Machines Corporation, Armonk, N.Y., USA, the assignee of the instant Patent Application and the disclosure of which is incorporated herein by reference, discloses a process for fabrication of a large area laminate magnet with a significant number of perforated holes, integrated metal plate(s) and electrodes for electron and electron beam control.
The invention is a novel low temperature sintering aid for ferrites and process for metal/magnetic-ceramic laminate with through-holes.
Therefore, one purpose of this invention is to provide a low temperature sintering aid for a magnetic-ceramic and a process that will form metal/magnetic-ceramic laminate.
Another purpose of this invention is to provide a low temperature sintering aid for a magnetic-ceramic and a process that will provide metal/magnetic-ceramic laminate with through-holes.
Yet another purpose of this invention is to use the metal/magnetic-ceramic laminate as a mask to create an image on at least one glass plate to form multi-phosphors (red, green, blue) material which receives an electron beam to create a display.
Still another purpose of this invention is to provide a low temperature sintered ferrite structure through which one or more collimated beam(s) of electrons can be formed using the ceramic/magnetic laminate.
Yet another purpose of this invention is to provide a low temperature sintered ferrite structure that can be used with any electron sensitive process.
Still yet another purpose of the invention is to provide a laminated metal/magnetic-ceramic that has a plurality of openings for guiding electrons and/or electron beams.
Still yet another purpose of the invention is to have a sintering aid in metal/magnetic-ceramic structure to allow lower temperature sintering.
Therefore, in one aspect this invention comprises a process of forming unsintered metal/ferrite laminate magnet, comprising:
(a) forming at least one opening in an metal sheet having a first surface and a second surface,
(b) securing at least one dielectric layer to at least a portion of said first surface of said metal sheet,
(c) securing at least one ceramic magnet layer containing at least one low temperature sintering aid to at least a portion of said at least one dielectric layer,
(d) forming at least one opening through said ceramic magnet layer and said dielectric layer, such that at least a portion of said opening overlaps at least a portion of said opening in said metal sheet, and thereby forming said unsintered metal/ferrite laminate magnet.
In another aspect this invention comprises a ceramic-metallic magnet comprising at least one ceramic-magnetic sheet, wherein said sheet has at least one low temperature sintering aid.
In still another aspect this invention comprises a ceramic-metallic magnet comprising at least one ceramic magnet sheet, wherein said sheet has at least one low temperature sintering aids and at least one adhesion promoter to form a metal-to-magnetic-ceramic layer adhesion.
In yet another aspect this invention comprises a process of forming unsintered metal/ferrite laminate magnet, comprising:
(a) forming at least one first opening in an metal sheet having a first surface and a second surface,
(b) securing at least one dielectric layer to at least a portion of said first surface of said metal sheet,
(c) securing at least one ceramic magnet layer containing at least one low temperature sintering aid to at least a portion of said at least one dielectric layer,
(d) forming a second opening using said first opening as a guide, such that at least a portion of said second opening overlaps at least a portion of said first opening in said metal sheet, and thereby forming said unsintered metal/ferrite laminate magnet.
In still yet another aspect this invention comprises a process of forming a sintered metal/ferrite laminate magnet, comprising:
(a) forming at least one opening in an metal sheet having a first surface and a second surface,
(b) securing at least one dielectric layer to at least a portion of said first surface of said metal sheet,
(c) securing at least one ceramic magnet layer containing at least one low temperature sintering aid to at least a portion of said at least one dielectric layer,
(d) forming at least one opening through said ceramic magnet layer and said dielectric layer, such that at least a portion of said opening overlaps at least a portion of said opening in said metal sheet, and sintering the same to form said sintered metal/ferrite laminate magnet.
In still another aspect this invention comprises a process of forming a ceramic-metallic magnet, comprising mixing at least one ceramic material, at least one metallic material and at least one low temperature sintering aid and sintering said mixture at a temperature of between about 400xc2x0 C. and about 1000xc2x0 C.